You probably don't NEED to know this, but it's interesting, and one of those things that one day you may actually benefit from the knowledge, and not necessarily even in relation to anything nautical.
There's a surprising amount of electrical science behind the simple concept of a boat floating in the sea. But when they hook up to shore power then things can get really bad if they don't have a simple device called a galvanic isolator fitted in the ground/earth wire.
This video explores the science and shows how a simple galvanic isolator is made.
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